1. Technical Field
The present invention relates to a light emitting element, a light emitting device and an electronic apparatus.
2. Related Art
An organic electroluminescent device (commonly called an organic EL element) is a light emitting element having a structure in which at least one layer of a luminescent organic layer is interposed between an anode and a cathode. In such a light emitting element, by applying an electric field between the cathode and the anode, electrons are injected from the cathode side into the light emitting layer and, along with this, holes are injected from the anode side, excitons are generated by the recombination of the electrons and the holes in the light emitting layer, and, when the excitons return to a ground state, the energy portion thereof is released as light.
The luminance life span in the above light emitting elements shows a tendency to vary according to the luminescent color emitted as light by the light emitting layer, and it is known that, specifically, the shorter the wavelength of the luminescent color, the shorter the life span.
For example, as one of the causes of this tendency, the following may be considered.
That is, it has been found that the shorter the wavelength of the luminescent color of the light emitting layer provided in the light emitting element, the easier the balance of the carrier (the holes and the electrons) flowing inside the light emitting element is lost and the stronger the tendency to excessively generate the carrier, as the use time of the light emitting element increases. For this reason, in a case where one or both of a hole transporting layer and an electron transporting layer are provided, for example, to be adjacent to the light emitting layer, in the above layers, there is a tendency for electrons or holes which have come through the light emitting layer to be injected, and, as a result, it is supposed that the degradation of the configurational material configuring the above layer is promoted.
As a configuration of the light emitting element solving the above problem, there has been proposed a configuration provided with a light emitting layer emitting red luminescent color of a longer wavelength in addition to a light emitting layer emitting (blue) luminescent color of a short wavelength.
That is, it has been proposed that, by configuring the light emitting element to be provided with a plurality of layers emitting short wavelength luminescent color and layers emitting long wavelength luminescent color as light emitting layers, a lengthening of the life span of the light emitting element is achieved (for example, refer to JP-A-2007-115626).
However, because long wavelength luminescent color (for example, red) is also naturally emitted from the light emitting element having the above configuration, in a case where it is necessary to set only short wavelength luminescent color (for example, blue) as the luminescent color emitted by the light emitting element, since there is a need to provide a color filter absorbing long wavelength luminescent color, there are problems in that the element configuration of the light emitting element becomes complicated and this leads to an increase in the number of processes when manufacturing the light emitting element.